Demography is destiny. It’s an old idea but it remains as true as ever, despite the fact that it doesn’t get anything like the attention it deserves. It’s not hard to see why: not only is there a crowded agenda of more immediate and obvious threats to our collective security at present, but you are likely to be dismissed as an eccentric “neo-Malthusian” if you raise the topic.

However, a recently released report by the UN serves as an uncomfortable reminder that, although the long-term rate of population increase may be slowing, we are still likely to end up with about nine billion people by about 2050. As the authors helpfully point out, population increase over the next 50 years is likely to be more than twice the current population of China. And China, as we know, is now the biggest producer of climate changing CO2 emissions, and currently disappearing beneath a toxic fog of its own making.

The tentative good news is that China’s population trends are actually moderately encouraging from a global perspective, which is the only perspective that actually makes sense when thinking about demography, of course. Indeed, a pretty good argument can be made that no country has actually done more to combat climate change than China: without the widely criticised one child policy, it is estimated that there would be 4-500 million more people in China that there already are, and climate change would be more advanced as a consequence.

China also highlights a critical problem with the actual make-up of nationally-based populations. In China’s case the growing imbalance between men and women threatens social harmony as men without mates vent their frustrations. So called “population bulges” raise similar sorts of challenges elsewhere, as large numbers of young men with little chance of finding rewarding employment seek other outlets for their energies and ambitions.

It is surely no coincidence that some of the world’s most intractable trouble spots also have powerful demographic and economic drivers. Palestine is perhaps the quintessential case in point. Elsewhere, fertility rates show little sign of decreasing and the capacity of governments in sub-Saharan Africa to provide work - let alone a sustainable environment - for a rapidly expanding population looks remote. Is it any wonder that so many risk everything in the hope of making a better life in Europe?

Europe is, of course, being transformed by such long-run demographic processes as a result. The declining birth rates of the indigenous populations of Western Europe when combined with large scale immigration, and the higher fertility rates of many of the arrivals, is inevitably changing the make up of European populations. At one level, this is arguably a good thing as an ageing Europe attracts eager young workers. But as the rise of the far right and domestically-generated terrorists in Europe reminds us, it is not a simple process to manage.

Nor is it without its paradoxes and contradictions. In the same week that the UN highlighted the big demographic picture, we learned that doctors in Sweden had pioneered the world’s first successful womb transplant. While details were sketchy, the cost has been estimated to be in excess of $500,000 for each procedure. Desires clearly don’t get much more fundamental than the urge to reproduce – or to make money, the cynical might say – but this does seem to say something unfortunate about our collective priorities and the value of life in different parts of the world.

I know from painful personal experience that such observations will win few friends. When I pointed out to a colleague that no matter how much recycling or solar-panelling he undertook, he’d never make as big a contribution to the environment as those of us who practice a no child policy, he didn’t speak to me for months. Reproduction remains a terribly sensitive topic and one that the overwhelming majority of the population has a personal stake in. Trying to encourage a rational debate about babies – especially white ones – is not for the faint-hearted.

The idea that we as a species are the principal cause of the planet’s problems is not a happy one nor the basis for an election-winning platform, for that matter. And yet it is not possible to think of a single global public policy or security issue that might look rather different if the world’s population was say three billion rather than seven – let alone nine. It’s not just that we’re rapidly wiping out so many other species that should concern us. The conditions that sustain our own kind are also jeopardised by our inability to limit our own numbers. If we can’t do something about it, the natural environment probably will.